What is the significance of Exodus 29:20?

… and you shall kill the ram and take part of its blood and put it on the tip of the right ear of Aaron and on the tips of the right ears of his sons, and on the thumbs of their right hands and on the great toes of their right feet, and throw the rest of the blood against the sides of the altar. (Exodus 29:20)

This was part of the ordination of Aaron and his sons—the ceremony whereby they were sanctified and appointed as priests. The same ceremony is also described in Exodus 29:20.

To an Old Testament Israelite, the different parts of the body were all symbolic of different aspects of life. So when we see something like this, we need to figure out how it would have been understood at the time.

The ear lobe stood for the ear: hearing the word of God

The thumb stood for the hand: doing the work of God

The toe stood for the foot: walking in the way of God

This ceremony was teaching them that to be priests in God’s house they had to be careful to listen to God, use their hands in his service, and walk in his ways. Presumably it was too messy to smear blood on the whole ear, whole hand and whole foot. So a small part was chosen to make the point. Being a priest was a whole lifestyle, it was not just a 9–5 job. Whenever they used their ears, hands and feet, they were to use them for God.